In the foodstuffs industry, containers of various sizes, shapes and compositions are utilized to hold a variety of food products. One common practice is to enclose the contents within a cardboard (or like material) box, with or without a flexible treated paper or plastic liner. Reclosing the box does not, however, effectively reseal the contents and freshness is difficult to maintain. Another technique is to provide a thin paper or plastic bag having a shape corresponding generally to a stack of food items, such as crackers, which is subsequently sealed. One or more of such bags is then inserted within an outer container or box. In most instances, the bag is unsealed, and often ripped open, and as food items are removed, the upper end of the liner or bag is rolled upon itself to form a smaller package. Again, the mere rolling down of the open portion of the bag does not provide a good seal, and the further enclosure within a box does not measurably improve the seal.
In accordance with the present invention, a thin film, self-supporting but collapsible bag is provided for holding food or other items. More specifically, a container is provided wherein a major portion of the length of which comprises a plastic thin film peripheral sidewall. Thicker upper and lower portions of the peripheral sidewall provide the required rigidity to support a removable lid, and to support the container in a normally upright position. However, axial pressure applied to either the top or bottom (or both) of the container will result in partial collapse of the container, to the extent permitted by the remaining contents.
In one exemplary embodiment, the container comprises a unitary extrusion, subsequently blow-molded, for example, to form a container having an open end and a closed end. In this exemplary embodiment, the container has a generally cylindrical shape from top to bottom, with a relatively wide mouth at the open end thereof. A thickened lower portion of the peripheral sidewall is provided which merges with a thickened bottom wall. At the upper, open end of the container, another thickened area is provided which includes means for receiving a removable lid or cover. In this regard, the upper thickened area may have a slightly smaller diameter than the remaining peripheral sidewall portion of the container, so that the removable lid or cover, when applied, will not extend radially beyond the container body to any significant degree.
It will be understood by those of ordinary skill in the art that the removable lid or cover may be of the snap-on or screw-thread type, and the profile of the upper thickened portion of the sidewall will be provided with annular ribs or screw threads, as appropriate, depending on the type of closure employed.
Variations in the lower areas of the container construction are also within the scope of the invention. For example, the lower, thickened area of the peripheral sidewall may be omitted, so that the thin walled peripheral side wall joins directly, or merges with a thickened bottom wall.
In another alternative configuration, the bottom wall may be thickened only in a central portion thereof.
In still another arrangement in accordance with the subject invention, the upper and lower thickened portions of the peripheral sidewall may be provided with radially outwardly extending peripheral beads which, upon collapse of the thin film sidewall portion, can be snapped together to maintain the container in this collapsed position, until the respective upper and lower portions are pulled apart to, for example, refill the container.
It will also be appreciated that the cross-sectional shape of the container may be varied, e.g., it may be circular, oval, rectangular, etc.
Other variations are also within the scope of the invention. For example, patterns, such as a "quilted" pattern, may be incorporated into the production of the thin walled area of the peripheral sidewall to add a measure of rigidity to this area of the container, but without eliminating the otherwise desirable collapsibility feature.
As noted above, a preferred process of forming containers in accordance with this invention involves the extrusion of a tubular parison between a pair of separated mold halves, the parison having been extruded to provide upper and lower areas with increased thickness as compared to the major peripheral portion of the sidewall. Thereafter, the mold halves, which are formed generally to provide the desired container shape, are closed and the parison blown into engagement with the interior surfaces of the mold. The upper and lower ends of the molds are provided with more detailed surfaces designed to provide the exact structural configuration of the thickened areas of the container.
It will thus be seen that the present invention provides a unitary, collapsible container which nevertheless has the necessary rigidity to be normally self-supporting, and to receive a removable lid or cover. The collapsibility feature enables the container to be reduced in size as the container contents are removed, to thereby expel excess air and, at the same time, provide increased compactness. It will, of course, be appreciated that the container may be extended and collapsed repeatedly during use, and particularly when the container is utilized for general storage purposes, i.e., used over and over again, as opposed to being discarded after a first use. In view of this construction, it is also possible, at least in some circumstances, to eliminate the need for exterior rigid containers.
Further objects and advantages of the invention will become apparent from the detailed description which follows.